tests: switch from nose to pytest

.gitlab-ci.yml

@@ -41,13 +41,13 @@ test:mypy:
     - pip install -r requirements-types.txt --quiet
     - mypy app
 
-test:nose:
+test:pytest:
   script:
     - cp config.yaml.example config.yaml
     - apt update && apt install build-essential
     - pip install -r requirements.txt --quiet
-    - pip install nose
-    - DISABLE_METRICS=true nosetests tests
+    - pip install pytest
+    - DISABLE_METRICS=true pytest tests
 
 test:pylint:
   script: